Armor and safe plate.



S. S. WAL

ARMOR AND SAP TB.

APPLIUATION FILED FEB. 5, 190a.

1,09%573. Patented May19,1914.

wrmzssss INVENTOR 'fi-glmllas v kPwmQQ UNITED STATES PATEN'I. OFFICE.

SAMUEL S. WALES, F MUNHALL, PENNSYLVANIA, ASSIGNOR- TO CARNEGIE STEELCOMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF NEW JERSEY.

Amazon mm sass PLATE.

Specification of Letters latent.

Application filed February 5, 1908. Serial No. 414,350.

the following is a full, clear and exact dey scription, re rencebeinghad to the accompanying drawings, iii-which Figure l is a sectionillustrating the fracture of armor plate embodying my invention,and-Fig. 2 is a similar View showing another form.

My invention relates to face-hardened armor plates, and vault or safeplates, and is designed to provide an improved plate which will affordhigher ballistic resistance, and in which the face-hardened portion isof more uniform chill or hardness than in previous plates of thischaracter.

To that end my invention consists in a face-hardened plate having itsface-hardened layer of substantially uniform hardness, the body orbackof the plate'having substantially uniform characteristics, and theplate also having a third intermediate layer between the face-hardenedportion and the back, said intermediate layer being in My improved asoft annealed condition. plate, therefore, while made integral possessesthe characteristics of a compound plate,- in that it consists of threedifferent layers having diflerent characteristics, each layerbeing'substant-ially uniform throughout its depth or thickness, and allthree layers being in molecular contact with each other, thus avoidingthe disadvantages of compound plates.

In obtaining my improved plate, my process departs from p'r-ior methodsor processes,

particularly in the stepof heating prior to quenching forwater-hardening. Heretofore in this step of the process as used inpractice, the plate has been bedded in loam .or similar material, whichcovers the back and all the edges of the plate, leaving the face to behardened exposed. The face of the plate is exposed to the heat of thefurnace, while the other parts of the plate are protected by the loam,and this face is raised to about 850 to 950 centigrade. During thisheating, the body of the plate is heated by conduction from the face tosuccessively lesser degree from the face to the back, the back'beingusually about 550? to 600 centigrade. The plate is then removed fromthefurnace and water sprays "directed against, both faces, This givesthe final hardness to the face of the plate, and at the same t me, thebody of the plate is softened or annealed by reason of its temperaturebeing in the range in which water annealmgt-akes place. The strength ofthe bod of the plate is decreased by this treatmen and this can not beremedied, it being thev final treatment. This prior method of heatingand quenching produces a plate having a face-hardened portlon with themaximum hardness at or near the surface thereof, this hardnessdecreasing gradually through the chilled portion. From the lower part ofthe chilled portion, the metal changes gradually in 1ts characteristicsthrough the body portion of the plate to its back: This body portionmerges into the face-hardened of chilled portion through a crystalline'structure, which gradually becomes mixed with the chllled fiber, or softannealed portion, the latter increasing successively toward the backuntil at the back there is no crystalline structure. In other words,starting at the back-of the plate, there is a soft annealed portion orfibrous structure whichmerges into the facehardened'portion by a. adualincrease in hardness until the chil ed or undrillable.

portion of the plate is reached. In, these previous plates, there wereno separate layers each having substantial uniform characteristicsthroughout the layer and each differing from the other layers as to suchcharacteristics. In other words, these plates varied continuously fromback to front as to thedegree of hardness and tensile strength, thoughnot necessarily uniformly. This character of plate is the result of theordinary heating for face-hardening, in which the entire plate is heatedto a greater or less degree, this heat decreasing from the front to theback of the plate continuously. Owing to this heating of the entire bodyof the plate, the main body portion is waterannealed at the same timethat the face is hardened by the quenching, and consequently, thewater-annealed portion at the back merges gradually into thewater-hardened portion through successive portions. This treatment willobviously remove or largely modify the effect of any former heattreatment which may have been beneficial to thebody of the plate, byraising its tensile strength or toughening It, as it will Patented May19, 1914.

In the manufacture of my improved plate, the face to be hardened isexposed in a fur-.

nace, directly to the heat, while the edges are protected by anyconvenient refractory material so as to force the heat to penetrate fromthe front surface only. At the same time the back is exposed to apositive cooling effect such as a spray of water, steam, or othercooling fluid, which is forced against it. The-surface to be hardened isthereby raised to a temperature where water-hardening takes place in thenext or waterquenching operation, while the main body of the plate ismaintained at such a temperature that no changes take place over thecondition in which the material was left by its immediately precedingmetallurgical treatment.

Between the portion to be water hardened and the main body or back ofthe plate there will be a thin layer where the temperature changes fromthe water-hardening range to the temperature where no action takes placein quenching. This thin layer of the plate will consist of soft metal,since its temperature at the time of quenching has been such that it isannealed during this step. This soft intermediate layer is connectedwith the face and the back or body by very thin laminae, wherein themetal is changing in characteristics to that of the face and back.

My improved plate comprises a face-hardened portion, in which thehardness is substantially uniform by reason of the uniformity oftemperature therein, and by'reason of the heating being practicallylimited to this portion of the plate, so that the total heat to beextracted is relatively small and because the inner surface of theheated portion is in molecular contact with the cooled back, which willextract the heat therefrom very rapidly, so that when this plate isfinally quenched the heat is extracted from the hot surface bydirectcontact with the water or cooling fluid, and also from the backportion of the heated layer by conductionthrough the cooled back, whichis also in contact With the cooling fluid. 'If this face-hardenedportion is four inches thick, the hardening operation amounts to thequenching of a four-inch plate, instead of a plate of the full thicknessof the plate treated, which in this case would be eight or ten inches vMy plate comprises a strong back portion, which maintains thecharacteristics imparted thereto by the last metallurgical treatmentprevious to heating for hardening, ow-

ing to the fact that the cooling of the back of the plate has preventedits temperature being raisedto a point where any annealing can takeplace, eitherduring the heating process or during the subsequentquenching. These two portions of the plate are connect ed by acomparatively thin layer wherein the heat is changing fromthetemperature "at which water-hardening takes place to that of the mainbody or back of the plate. This portion will obviously be annealed to asoft condition.

The above described product will thus furnish a plate consisting ofthree principal layers or strata, as seen in Fig. 1, which shows asection broken tl'irough the plate, the main body or back of the plate 2being in substantially the same condition that it was before thistreatment,the face or waterhardened portion 3 being chilled to thedesired hardness, and an intermediate layer 4 consisting of a soft orannealed metal between and connecting the two above mentioned layers.The division line between the middle layer and the main body or back ofthe plate may not be distinctly visible to the eye where the main bodyor back of the plate was annealed to the same condition before heatingfor water-hardening as this strip will be after process of heating forwaterhardening, but this ,will in no way interfere with the invention.

In case the body or back of the plate has been annealed to a softcondition, but still harder than this soft strip mentioned, the line ofdemarcation may not be visible to the eye, as is the case of Fig. 2showing a. section broken through the plate, but can be detected byphysical tests taken successively from the back to the face of theplate. If the main body or back of the plate in its immediatelypreceding metallurgical treatment has been left in a condition whosestructure differs radically from that of the soft annealed strip, b'othdivision lines will be visible to the eye, as in Fig. 1. My plate,therefore, contains all the advantages claimed for compound platcs madeup of several layers of distinct metal, while avoiding theirdisadvantages, as the laminations are induced in a homogeneous metal bydefinite heat treatment, and not by being built up and welded together,nor by being cast in successive layers. The body of the plate is kept inits condition prior to heating for layer of fibrous structure, and anunannealed back or body in the unannealed condition imparted theretoprior to heating the plate for hardening its face, and forming the majorportion of the thickness of the plate; substantially as described.

2. A compound face-hardened armor or vault plate integrally formed,having three layers, namely, a face-hardened layer, an unannea led' backportion constituting the greater thickness of the plate and a thinintermediate layer of annealed softer material; substantially asdescribed.

3. A compound face-hardened armor or vault plate integrally formed,having three layers, namely, a face-hardened layer, an unannealed backportion constituting the greater thickness of the plate and a thininnealed back &

termediate layer of annealed softer metalhaving less tensile strength.than the unanportion; substantially as described.

4. A compound face-hardened armoror vault plate formed integrally andhaving three distinct layers constituting a facehardened layer, anunannealed layer forming the back or body portion of the plate and athin layer of soft annealed material of less tensile strength than theunannealed back layer; substantially as described.

In testimony whereof, I have hereunto set my hand.

S. S. WALES. \Vitnesses:

HOWARD L. CAMPBELL,

W. H. CORBEI'I.

